PubMed Health⌕ Search

Biomedical subjects

C Charland

Publications and source records attributed to C Charland.

15 recordsLinked to original sources
PubMed2000

Activation of the p38 mitogen-activated protein kinase pathway arrests cell cycle progression and differentiation of immature thymocytes in vivo.

The development of T cells in the thymus is coordinated by cell-specific gene expression programs that involve multiple transcription factors and signaling pathways. Here, we show that the p38 mitogen-activated protein (MAP) kinase signaling pathway is strictly regulated during the differentiation of CD4(-)CD8(-) thymocytes. Persistent activation of p38 MAP kinase blocks fetal thymocyte development at the CD25(+)CD44(-) stage in vivo, and results in the lack of T cells in the peripheral immune system of adult mice. Inactivation of p38 MAP kinase is required for further differentiation of these cells into CD4(+)CD8(+) thymocytes. The arrest of cell cycle in mitosis is partially responsible for the blockade of differentiation. Therefore, the p38 MAP kinase pathway is a critical regulatory element of differentiation and proliferation during the early stages of in vivo thymocyte development.

Animals↗
PubMed1999

A model for the origin of TCR-alphabeta+ CD4-CD8- B220+ cells based on high affinity TCR signals.

The origin of TCR-alphabeta+ CD4-CD8- cells is unclear, yet accumulating evidence suggests that they do not represent merely a default pathway of unselected thymocytes. Rather, they arise by active selection as evidenced by their absence in mice lacking expression of class I MHC. TCR-alphabeta+ CD4-CD8- cells also preferentially accumulate in mice lacking expression of Fas/APO-1/CD95 (lpr) or Fas-ligand (gld), suggesting that this subset might represent a subpopulation destined for apoptosis in normal mice. Findings from mice bearing a self-reactive TCR transgene support this view. In the current study we observe that in normal mice, TCR-alphabeta+ CD4-CD8- thymocytes contain a high proportion of cells undergoing apoptosis. The apoptotic subpopulation is further identified by its expression of B220 and IL2Rbeta and the absence of surface CD2. The CD4-CD8- B220+ phenotype is also enriched in T cells that recognize endogenous retroviral superantigens, and can be induced in TCR transgenic mice using peptide/MHC complexes that bear high affinity, but not low affinity, for TCR. A model is presented whereby the TCR-alphabeta+ CD2- CD4-CD8- B220+ phenotype arises from high intensity TCR signals. This model is broadly applicable to developing thymocytes as well as mature peripheral T cells and may represent the phenotype of self-reactive T cells that are increased in certain autoimmune conditions.

Amino Acid Sequence↗
PubMed1997

Role of extracellular signal-regulated protein kinases in apoptosis by asbestos and H2O2.

Stimulation of cell signaling cascades by oxidants may be important in the pathogenesis of pulmonary and pleural diseases. Here, we demonstrate in rat pleural mesothelial cells that apoptotic concentrations of crocidolite asbestos and H2O2 induce phosphorylation and activation of extracellular signal-regulated protein kinases (ERK). Activation of c-jun-NH2-terminal protein kinases (JNK)/stress-activated protein kinases was also observed in response to H2O2. In contrast, asbestos caused more protracted activation of ERK without JNK activation. Both H2O2- and asbestos-induced activation of ERK was abolished by catalase. Moreover, chelation of surface iron from crocidolite fibers or addition of N-acetyl-L-cysteine prevented ERK activation and apoptosis by crocidolite, indicating an oxidative mechanism of cell signaling. The MEK1 inhibitor PD-98059 abrogated asbestos-induced apoptosis, confirming a causal relationship between ERK activation and apoptosis. These results suggest that distinct cell-signaling cascades may be important in phenotypic responses elicited by oxidant stresses.

Acetylcysteine↗
PubMed1993

Proliferative index of human luteinized granulosa cells varies as a function of ovarian reserve.

OBJECTIVE: We examined whether the proliferative index of luteinized granulosa cells, as determined by flow cytometry, varied as a function of a woman's ovarian reserve, as reserve, as reflected by follicular-phase day 3 serum follicle-stimulating hormone. STUDY DESIGN: This prospective cohort study consisted of 19 women of similar chronologic age preparing for in vitro fertilization-embryo who met specific day 3 serum follicle-stimulating hormone criteria. The "low follicle-stimulating hormone" group consisted of 11 women with day 3 serum follicle-stimulating hormone levels < or = 6 IU/L. The "high follicle-stimulating hormone" group consisted of eight women with day 3 serum follicle-stimulating hormone levels > or = 18 IU/L. A total of 56 preovulatory follicles containing > or = 10(4) luteinized granulosa cells were examined by flow cytometry. The low follicle-stimulating hormone group was compared with the high follicle-stimulating hormone group to examine proliferative index as a function of serum day 3 follicle-stimulating hormone levels. RESULTS: The low follicle-stimulating hormone group had a greater proliferative index (11.1% +/- 0.4%) than did the high follicle-stimulating hormone group (8.3% +/- 0.6%), p < 0.001). This study demonstrates that in spite of the same chronologic age, luteinized granulosa cells from preovulatory follicles of women with day 3 serum follicle-stimulating hormone levels > or = 18 IU/L have a 25% decreased proliferative index compared with luteinized granulosa cells from women with day 3 serum follicle-stimulating hormone levels < or = 6. CONCLUSIONS: This suggests that granulosa cell proliferation is influenced by ovarian reserve and may explain in part the more favorable response to ovulation induction protocols that younger women demonstrate compared with women of more advanced reproductive age.

Adult↗
PubMed1993

Reference ranges for lymphocyte subsets in pediatric patients.

Peripheral blood lymphocyte subset reference ranges were examined in a large group (N = 130) of healthy pediatric patients ranging in age from 1 month to 17 years. All samples were stained with monoclonal antibodies, processed with a whole blood lysis technique, and analyzed on a flow cytometer. Data analysis demonstrated statistically significant changes in most lymphocyte subsets at age 3 years. The relative and absolute numbers of total lymphocytes, CD2, CD4, and CD19 cells; absolute numbers of CD3 and CD8 cells; and CD4/CD8 ratios were high at birth, decreased during early childhood, and closely approximated adult reference values after age 3 years. The relative numbers of CD8 lymphocytes were low in early childhood and then rose to adult values after 3 years of age. The relative percentage of CD3 cells remained stable over all ages studied. Although "adult" lymphocyte subset reference ranges may be similar to those in children older than 3 years, age-adjusted reference ranges should be used for the early childhood period.

Adolescent↗
PubMed1990

Isolation of large numbers of enriched human megakaryocytes from liquid cultures of normal peripheral blood progenitor cells.

Investigations linking human megakaryocyte development and cell biology have been hindered by an inability to obtain large, relatively pure megakaryocyte cell preparations from in vitro stem cell cultures. We report here that such preparations can be generated from liquid cultures of normal human peripheral blood mononuclear cells stimulated by a serum source of megakaryocyte colony stimulating activity (Meg-CSA, the 0% to 60% ammonium sulfate protein fraction of aplastic canine serum). Adherent-depleted peripheral blood mononuclear cells are suspended at 5 x 10(5) to 10(6) cells/mL in supplemented liquid culture medium, platelet-poor human plasma 20% (vol/vol) and 1 to 2 mg/mL serum Meg-CSA protein. After 12 to 14 days of incubation, megakaryocytes constitute 3.0 +/- 2.9% (mean +/- SD, n = 8) of the unseparated cultured cell population. Megakaryocytes can be enriched by counterflow centrifugal elutriation to a purity of 58 +/- 14% (+/- SD) with a recovery of 13 +/- 7% and a viability of 67 +/- 19%. This algorithm results in the average isolation of approximately 3 x 10(5) enriched megakaryocytes from a 100-mL starting volume of peripheral blood. Cultured megakaryocytes exhibit normal light and ultrastructural morphology by Wright-Giemsa staining and electron microscopic analysis. After a 12-day culture interval, enriched megakaryocyte preparations exhibit morphologic stage distributions that are similar to normal human marrow. Stage distributions move rightward with culture duration indicating partial synchrony of megakaryocyte maturation. On cytospin preparations, megakaryocyte diameter averages 30.2 +/- 1.5 microns and increases with maturation stage. Flow cytometric analyses demonstrate the expression of platelet glycoproteins (GP) Ib and IIb/IIIa by the cultured megakaryocytes. The modal ploidy of the enriched cells at day 12 of culture is 16N and most remaining megakaryocytes are 8N or 32N. Liquid culture of serum Meg-CSA-stimulated human peripheral blood mononuclear cells represents a valuable investigative tool that should permit studies of human megakaryocyte biology that have not been possible in the past.

Algorithms↗
PubMed1988

Alteration of rat Kupffer cell function following mitomycin-C administration.

Cancer chemotherapeutic agents modify the human immune system in diverse ways including both immunosuppression and immunostimulation. We evaluated the effects of mitomycin-C on rat Kupffer cell phagocytosis, C3b receptor binding, and lysosomal enzyme activity. Kupffer cell cultures were greater than 95% pure. Phagocytosis of IgG-coated sheep red blood cells was demonstrated by 84% of control cells but by only 25% of cells isolated two weeks following mitomycin-C administration (p less than 0.0005). This depression in phagocytic ability had returned to control levels by four weeks posttreatment. Similarly, C3b receptor binding of IgM and complement coated sheep red blood cells was observed in 88% of control Kupffer cells, but declined to 47% at two weeks after drug administration (p less than 0.005) and returned to normal after four weeks. Lysosomal enzyme activity was not impaired by mitomycin-C. Histologically severe ulceration of the colon of treated animals was seen one and two weeks after drug administration, but healed by four weeks post-mitomycin-C treatment. Depression of macrophage function as a consequence of cancer chemotherapy may have important clinical consequences in host defense against bacteria and tumor metastases.

Animals↗
PubMed1985

Effects of penicillamine on serum immunoglobulins and immune complex-reactive material in primary biliary cirrhosis.

Although penicillamine is used in the treatment of primary biliary cirrhosis, its mechanism of action in this disease is unknown. As an immunologic action had been attributed to the drug, we investigated whether penicillamine might alter serum immunoglobulin levels or immune complex-reactive material in patients with primary biliary cirrhosis. Immunoglobulin levels and immune complex reactivity were measured and clinical tests were performed in 53 consecutive patients entering a double-blind randomized trial of 750 mg vs. 250 mg of penicillamine. Measurement of immune complex reactivity was determined by laser nephelometry, 125I-C1q binding, and Raji cell assays. Immune complex reactivity was detected by at least one assay in 75% of patients tested before treatment. Sixty-two percent were positive in the C1q assay, 28% in the Raji cell assay, and 39% by nephelometry. After therapy with either dose, we found no change in immune complex-reactive material by any assay. Concentrations of immunoglobulins G and M fell (p less than 0.05) after 12 mo of therapy. Concentrations of immunoglobulin A decreased (p less than 0.05) only in the high-dose group. Correlation was not consistent between results of immune complex assays and clinical liver tests. Although immunoglobulin levels fell during penicillamine therapy, no decrease in immune complex-reactive material was detected. The effect of penicillamine in primary biliary cirrhosis is not mediated through alteration of immune complex-reactive material.

Antigen-Antibody Complex↗
PubMed1979

Effects of sulfasalazine on selected lymphocyte subpopulations in vivo and in vitro.

Sulfasalazine has proven to be an effective agent in the therapy of inflammatory bowel disease (IBD). Despite long and widespread usage, the mechanism of action of this drug is still not understood. Several investigators have suggested that the drug might act as an immunosuppressant. To examine this possibility, an in vivo study was undertaken to ascertain any quantitative change in the circulating T cells, Ig-bearing B cells, and complement receptor-bearing lymphocytes (CRL) of patients before and during therapy with sulfaslazine. Concomitant responses to skin test antigens were also evaluated. In vitro studies with control cells were performed to determine the influence of sulfasalazine and its components (sulfapyridine or 5-aminosalicylic acid) on the extent of antibody-dependent cellular cytotoxicity (ADCC), as well as on the number of T cells and CRL. Results indicate that neither sulfasalazine nor either of its components quantitatively alters those subpopulations of circulating mononuclear cells studied in vivo or in vitro--nor are these compounds responsible for any functional inhibition of ADCC.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1979

Circulating Clq binding complexes in inflammatory bowel diseases.

To determine whether circulating immune complexes are present in the sera of patients with inflammatory bowel disease (IBD), a 125I-Clq binding assay was performed. Of the 55 IBD serum samples tested, the 24 ulcerative colitis samples demonstrated significant binding (33.1 +/- 8.3%, p = 0.02), whereas the 31 Crohn's samples bound essentially normal amounts (29.2 +/- 7.4%). A positive control group consisting of 27 patients with rheumatoid arthritis was also studied. Sera from 4 patients wiht IBD and colonic cancer when tested, bound 40.2 +/- 8.0% of the available 125I-Clq, while 10 patients with previous colectomies and ileostomies gave results similar to those of 15 healthy controls and 11 patients with irritable colon.

Antigen-Antibody Complex↗
PubMed1978

Skin test reactivity in inflammatory bowel disease in the United States and Czechoslovakia.

Inflammatory bowel disease (IBD) patients in the United States of America (USA) and Czechoslovakia (CSSR) were categorized by clinical, pathological, and radiological criteria as having Crohn's disease (CD) or ulcerative colitis (UC) and were tested with five skin test antigens [Candida, mumps, purified protein derivative (PPD), streptokinase-streptodornase (SK-SD), and trichophytin] at two different dilutions in an attempt to elicit some evidence of anergy. No significant differences were encountered between the USA and CSSR populations or between any patient group and its controls.

Allergens↗
PubMed1976

The subpopulations of circulating white blood cells in inflammatory bowel disease.

A detailed analysis of the species of lymphocytes was carried out in 58 patients with inflammatory bowel disease (IBD). These individuals were further divided into 31 with Crohn's disease (CD) and 27 with ulcerative colitis (UC). There were 13 CD patients with only small bowel involvement called "regional enteritis" and 18 who had some degree of colonic involvement called "ileocolitis". Similarly, the UC group was subdivided into 9 patients with disease confined to the rectosigmoid area called "proctosigmoiditis" and 18 with more extensive involvement called "universal colitis". We also studied 13 patients who had undergone previous colectomy and ileostomy and 78 healthy age- and sex-matched controls. Although there was no increase in the absolute number of lymphocytes in patients with ileocolitis and universal colitis, the percentage of these cells was decreased because of an increase in both polymorphonuclear leukocytes and monocytes. In IBD and its subgroups, mean T lymphocytes, determined by the sheep red blood cell rosette technique, were not significantly different from the controls either in percentage or absolute number. Furthermore, no difference was noted between UC and CD. However, there seems to be a subpopulation of patients with UC or CD whose T cells are reduced below 1 SD of the mean. There was also no difference in the number of immunoglobulin-bearing B cells in both diseases; however, when the B cells were enumerated by their ability to rosette with antibody-complement-coated sheep cells (EAC), we found a marked decrease in percentage (P less than 0.001) and absolute number (P less than 0.0005) relative to the control population. The decrease bore a direct relation to the severity of the disease process and, although more marked in patients with UC, was present in CD also.

B-Lymphocytes↗
PubMedDate not supplied

Elevated circulating immune complexes in primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC) is a syndrome of unknown etiology characterized by an association with inflammatory bowel disease in 50% or more cases. Since altered immunity, including circulating immune complexes, has been implicated in the pathogenesis of inflammatory bowel disease, we postulated that humoral immune mechanisms might also be important in the development of PSC. Therefore, as an initial step in testing this hypothesis, we examined sera of patients with PSC for the presence of circulating immune complexes by two independent methods: C1q binding and Raji cell assays. Twenty-four patients with PSC, 16 of whom had coexisting chronic ulcerative colitis, were prospectively selected by predefined biochemical, histologic, and radiographic criteria. Sixteen patients with inflammatory bowel disease and normal liver tests as well as six patients with extrahepatic biliary obstruction served as disease controls. Sera were positive for circulating immune complexes by at least one method in 80% (16/20) of patients with PSC; 70% (14/20 were positive by the Raji cell assay, 58% (14/24) by the C1q binding assay, and 45% (9/20) by both methods. Levels of circulating immune complexes by each assay were higher in sera from patients with PSC than in sera from healthy controls or patients with inflammatory bowel disease alone (p less than 0.01). There were no differences in the levels of circulating immune complexes or in the frequency of positive tests in PSC patients with or without associated inflammatory bowel disease. In addition, there was no difference between the Raji cell binding of sera from six patients with extrahepatic biliary obstruction and six healthy controls tested concurrently. These data are consistent with the hypothesis that immunologic mechanisms may be important in the pathogenesis of PSC.

Antigen-Antibody Complex↗
PubMedDate not supplied

Characterization of a new monoclonal antibody to rat macrophages and Kupffer cells.

We have characterized the cell and tissue binding specificity of a newly generated monoclonal antibody, Mab Ku-1, which shows selective reactivity with rat macrophages and Kupffer cells. The hybridoma secreting Mab Ku-1 was constructed by fusion of 8653 myeloma cells with spleen cells isolated from a mouse immunized with nonparenchymal liver cells coated with antihepatocyte antibodies. When binding was assessed by indirect immunofluorescence on frozen sections from normal liver tissue, Mab Ku-1 showed strong reactivity with Kupffer cells but was unreactive with hepatocytes, endothelial cells, bile ducts or lymphocytes. Both resident and activated macrophages bound Mab Ku-1. Reactivity in other tissues was compatible with specificity for macrophages. In the gut, scattered cells in the lamina propria were positive, whereas epithelial cells were negative. Individual cells in the lung were reactive. In the spleen, cells in the red pulp peripheral to germinal centers bound antibody. Reactivity of Mab Ku-1 to isolated Kupffer cells correlated with endogenous peroxidase activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of components immunoprecipitated by Mab Ku-1 from detergent lysates of Kupffer cells biosynthetically labeled with 35S-cysteine and 35S-methionine demonstrated that the reactive antigen was a peptide with an apparent molecular weight of 107 kD. This rat macrophage-reactive monoclonal antibody is a useful marker for identification of macrophage populations in tissue as well as in isolated cell populations.

Animals↗